As a bio-information measuring system to measure bio-information of a subject intermittently or continuously, a body fluid component measuring system that measures body fluid of the subject intermittently or continuously and displays a blood glucose level is known. Conventionally, so-called self-monitoring of blood glucose (SMBG), in which blood drawn by puncturing a fingertip or the like by a dedicated puncture device is measured by a blood glucose meter each time blood is drawn, has been widely used as a method for a diabetic to measure and manage the blood glucose level for himself/herself.
As an alternative, a body fluid component measuring system allowing continuous glucose monitoring (CGM), in which the blood glucose level of a subject is continuously monitored with a sensor positioned indwelling in a skin by making a puncture under the skin or the like with a needle disposed on a dedicated sensor unit, has recently been developed (see Japanese Application Publication No. 2002-526137, for example), and has already been put to practical use in Europe and America.
The body fluid component measuring system used for the CGM is composed of the sensor unit always mounted on a subject, a transmitting unit that is attached to this sensor unit and transmits a measurement signal in this sensor unit to the external, and a display device that calculates a blood glucose level based on the measurement signal transmitted from this transmitting unit and displays this blood glucose level. This system is such that the sensor unit is replaced with a new sensor unit at a frequency of about once every three days to one week.
The transmitting unit and the display device, on the other hand, are continuously used irrespective of the replacement of the sensor unit, and use over a long period is allowed by repeatedly carrying out charging or replacement of a battery.
However, it is undesirable that the monitoring of the blood glucose level of a subject is interrupted for a long time every time the battery mounted in the transmitting unit and the display device needs to be charged or replaced. On the other hand, it becomes possible to reduce the cumulative total value of the time for which the monitoring of the blood glucose level is interrupted by decreasing the charging frequency or replacement frequency of the battery mounted in the transmitting unit and the display device. However, in this case, the size of the battery mounted in the transmitting unit and the display device becomes large and therefore convenience decreases for the subject on which they are always mounted.
For such circumstances, in the body fluid component measuring system that measures body fluid of a subject intermittently or continuously and displays the concentration of a predetermined body fluid component, it is desirable to allow shortening of the time for which monitoring of the concentration of this body fluid component is interrupted without impairing convenience for the subject.